import threading
import time

def sing():
    while True:
        print('sing')

def study():
    while True:
        print('study')

if __name__ == '__main__':
    print('现在开始了')
    t1=threading.Thread(target=sing)
    t2=threading.Thread(target=study)

    t1.start()
    t2.start()

    while True:
        length=len(threading.enumerate())
        print('现在运行的线程数一共为{}'.format(length))

